Antenna radiator

ABSTRACT

Antenna radiator, consisting of two plate-like or film-like parts ( 1, 2 ) connected by their foot ends ( 11 ) to each other and to the supply connection of the antenna. To reduce especially current and voltage losses, the radiator parts are substantially wider at the foot ( 1 ) than at the tip ( 12 ).

This application is the National Stage of International ApplicationPCT/F100/00139 which was filed on Feb. 22, 2000 and designated the U.S.This International Application was published under PCT Article 21(2) inEnglish.

The present invention relates to an antenna radiator consisting of twoplate-like or film-like parts connected by their foot ends to each otherand also to the supply connection of the antenna.

For instance, the base transceiver stations of mobile telephone systemsuse dipole antenna systems comprising dipole antennas adapted for one ormore frequency ranges, e.g. 900 MHz and 1800 MHz. The antennas haverelatively narrow radiators which consist of two parts extending to bothsides of the supply point of the antenna. The antennas have been madee.g. by etching on a fiberglass circuit plate. The radiators of theantennas are relatively narrow.

Due to the high frequencies used in mobile telephone systems, thecircuit plate on which the antenna construction has been etched causesdissipation. The dissipation is mainly due to a large current flowing atthe foot of the radiator parts and to voltage losses occurring at thetips of the radiator parts. A drawback with present antennas is themagnitude of dissipation, which is a result of especially the fact thatthe radiator parts are narrow at the foot.

The object of the present invention is to eliminate the drawbacks ofprior-art solutions and achieve a radiator structure especiallyapplicable for use in base stations of mobile telephone systems. Theantenna radiator of the invention is characterized in that, especiallyto reduce current and voltages losses, the radiator parts aresubstantially wider at the foot than at the tip.

An embodiment of the invention is characterized in that the radiatorparts taper from the foot towards the tip.

When a radiator according to the invention is used, dissipation causedby the circuit plate is reduced because the wide foot part reduces thelosses due to the current flowing in the foot. In addition, due to theirnarrow shape, the tips have a small contact area, thus producing onlysmall voltage losses. Therefore, a good radiation efficiency isachieved.

In the following, the invention will be described in detail by the aidof an example with reference to the attached drawing, which presents anantenna with a radiator according to the invention, suited for use e.g.in a base transceiver station of the 900 MHz mobile telephone network.

The dipole antenna presented in the figure comprises a film-like dipoleradiator of electrically conductive material, consisting of two parts,an upper and a lower part 1, 2. The parts are connected together by anarrow metal strip 3. Placed behind the radiator 1, 2 is a reflector 4,whose length somewhat exceeds the height of the radiator. The radiator1, 2 and the strip 3 have been etched on a fiberglass circuit plate 5.The antenna is connected by a connecting cable 6 from the supply pointat the middle of the strip 3 to the receiver-transmitter apparatus of abase transceiver station.

The radiator parts 1, 2 are of a triangular shape and symmetric withrespect to each other so that the upper triangle points upward and thelower triangle 2 downward. Thus, each part 1, 2 tapers linearly from thefoot end 11 towards the tip 12. The side 13 in the direction of the mainbeam is inclined while the side 14 next to the reflector 4 is upright.

In the radiator of the invention, the current density is significantlysmaller than in prior-art solutions, especially at the foot 11 of theradiator parts 1, 2, where the current is largest, thanks to the widthof the foot end structure. As the current is diminished toward the tip,the radiator part 1 tapers linearly, so that the tip 12 of the radiator,which is the most sensitive area of the radiator in respect of theoperation of the antenna, is narrow. In addition, the tip 12 has a bluntshape to avoid interference.

It is obvious to a person skilled in the art that different embodimentsof the invention are not restricted to the example described above, butthat they may be varied within the scope of the claims presented below.

What is claimed is:
 1. A dipole antenna radiator comprising: twoplate-like or film-like radiator parts connected by their foot ends toeach other and to a supply connection of an antenna, the radiator partsbeing substantially wider at their foot ends than at their tips, whereinan edge of the radiator part on a side facing in a direction ofradiation is straight while an edge opposite the direction of radiationis inclined, or wherein the edge of the radiator part on the side facingin the direction of radiation is inclined while the edge opposite to thedirection of radiation is straight.
 2. The dipole antenna radiator ofclaim 1, wherein the radiator parts are tapered from their foot endtoward their tip.
 3. The dipole antenna radiator of claim 2, wherein theradiator parts are tapered substantially linearly from their foot endtoward their tip.
 4. The dipole antenna radiator of claim 1, wherein theradiator parts are connected to each other via a narrow strip-likeconnecting part, the supply connection of the antenna being fitted inconjunction with the narrow strip-like connecting part.
 5. The dipoleantenna radiator of claim 1, wherein the radiator is fitted on a circuitplate.